Centrifugal blowers known in the art typically include a housing having a compartment, an axial fluid inlet, and a radial fluid outlet. An impeller having a plurality of blades is disposed in the compartment of the housing. The blades are arranged around a rotational axis of the impeller and attached to a hub of the impeller for rotation therewith. Rotational movement of the impeller causes a flow of fluid received in the fluid inlet to flow in a radially outward direction in respect to the impeller to the fluid outlet. A shield may be provided in the fluid inlet to militate against inadvertent contact with the impeller and direct the flow of the fluid through the fluid inlet. The shield is typically stationary and a proximity of an edge of the shield to the rotating blades of the impeller can cause turbulence and noise.
In climate control applications such as heating, ventilating, and air conditioning (HVAC) systems of a vehicle, the centrifugal blowers are required to operate effectively and efficiently over a range of operating conditions. Different operating conditions of the system occur as a result of a desired mode and output of the system. Based on the desired mode and output, various vent doors within duct passages of the system are selectively opened and closed to direct the flow of fluid therethrough. Generally, each of the duct passages has a different flow resistance. The flow resistance, typically, is greatest in a floor mode, a heating mode and a defrost mode, and least in an air conditioning mode. In some instances, the flow resistance during the floor, the heating, and the defrost modes can cause an accumulation of pressure and fluid in the compartment.
It is desirable to produce a centrifugal blower including a shield that performs as a tunable guide device to minimize turbulence, noise, and a recirculation flow of the fluid at the fluid inlet of the housing.